My retreat, the "Can-Am Garage" is 12' x25' and it is an over sized shed.It was built by the previous owner and appears to have been an extension on a smaller shed.
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It is too small for a car / truck, but my 2 ATV trailer fits....mostly.
You learn to make the most of the space. Although to small for a garage with a car/truck, there is lots of space for my ATV and wood working.
My cave at the city house is a basement workshop - room for wood working, but lugging tools out to the driveway gets really old. Like everyone, I'll outgrow this. Perhaps in time for a retirement house.